Pneumonia is an infection in one or both of the lungs. Many germs, such as bacteria, viruses, and fungi, can cause pneumonia. You can also get pneumonia by inhaling a liquid or chemical. People most at risk are older than 65 or younger than 2 years of age, or already have health problems.

Symptoms of pneumonia vary from mild to severe. See your doctor promptly if you

Your doctor will use your medical history, a physical exam, and lab tests to diagnose pneumonia. Treatment depends on what kind you have. If bacteria are the cause, antibiotics should help. If you have viral pneumonia, your doctor may prescribe an antiviral medicine to treat it.

Preventing pneumonia is always better than treating it. Vaccines are available to prevent pneumococcal pneumonia and the flu. Other preventive measures include washing your hands frequently and not smoking.

NIH: National Heart, Lung, and Blood Institute

Definition (NCI_NCI-GLOSS)

A severe inflammation of the lungs in which the alveoli (tiny air sacs) are filled with fluid. This may cause a decrease in the amount of oxygen that blood can absorb from air breathed into the lung. Pneumonia is usually caused by infection but may also be caused by radiation therapy, allergy, or irritation of lung tissue by inhaled substances. It may involve part or all of the lungs.